Update 01.04.2022

build.gradle.kts

@@ -1,5 +1,5 @@
 plugins {
-    kotlin("jvm") version "1.4.32"
+    kotlin("jvm") version "1.6.10"
 }
 
 group = "ru.mipt.npm"

src/main/kotlin/demos/exceptions.kt

@@ -0,0 +1,15 @@
+package demos
+
+import java.io.IOException
+
+fun main() {
+    try {
+        val b: Nothing = throw RuntimeException("Oops")
+    } catch (t: IOException){
+        println(t.message + "_io")
+    } catch (t: RuntimeException){
+        println(t.message)
+    } finally {
+        println("caught")
+    }
+}

src/main/kotlin/demos/fileIO.kt

@@ -0,0 +1,22 @@
+package demos
+
+import java.nio.file.Files
+import java.nio.file.Path
+import kotlin.io.path.readLines
+import kotlin.io.path.useLines
+import kotlin.io.path.writeLines
+
+fun main() {
+    val myFile: Path = Files.createTempFile("ks_demo", ".txt")
+    myFile.writeLines((0..1000).map { it.toString() })
+
+    println(myFile)
+
+    val sum: Double = myFile.useLines {
+        it.drop(10).take(10).map { line ->
+            line.toDouble()
+        }.sum()
+    }
+
+    println(sum)
+}

src/main/kotlin/demos/integration.kt

@@ -0,0 +1,28 @@
+package demos
+
+import kotlin.math.PI
+import kotlin.math.cos
+import kotlin.math.pow
+import kotlin.math.sin
+
+fun integrate(range: ClosedRange<Double>, nPoints: Int = 100, f: (Double) -> Double): Double {
+    val points = DoubleArray(nPoints) { i ->
+        range.start + i * (range.endInclusive - range.start) / (nPoints - 1)
+    }
+
+    return points.sumOf { f(it) } * (range.endInclusive - range.start) / nPoints
+}
+
+fun ((Double) -> Double).integrate(
+    range: ClosedRange<Double>,
+    nPoints: Int = 100,
+): Double = integrate(range, nPoints, this)
+
+fun main() {
+    val res = integrate(0.0..PI, 500) { x -> sin(x) + cos(x) * x.pow(2) }
+    println(res)
+
+    val f = { x: Double -> sin(x) + cos(x) * x.pow(2) }
+
+    val res2 = f.integrate(0.0..PI)
+}

src/main/kotlin/demos/performance.kt

@@ -0,0 +1,9 @@
+package demos
+
+fun function(array: DoubleArray): DoubleArray {
+    return DoubleArray(array.size) { i -> array[i] + 1 }
+}
+
+fun main() {
+    println(listOf(1, 2, 3).asSequence().map { it * it }.map { it + 1 }.toList())
+}

src/main/kotlin/demos/primitives.kt

@@ -0,0 +1,9 @@
+package demos
+
+fun main() {
+    val array = doubleArrayOf(1.0, 2.0, 3.0)
+    val b: Double? = 1.0
+    val newArray: DoubleArray = DoubleArray(array.size) {
+        array[it] + (b  ?: 0.0)
+    }
+}

src/main/kotlin/lesson1/idiom2.kt

@@ -18,4 +18,7 @@ fun main() {
 
     /* recommended */
     val sum = (0..20).sum()
+
+    val intArray: IntArray = IntArray(20){ it }
+    intArray.sum()
 }

src/main/kotlin/lesson2/idiom13.kt

@@ -3,9 +3,10 @@ package lesson2
 fun printNotNull(any: Any) = println(any)
 
 val value: Int? = 2
+//val value: Int? by lazy{ 2 }
 
 fun main() {
-
+    //printNotNull(value) // Error
     if (value != null) {
         //not guaranteed to work with mutable variable
         printNotNull(value)

src/main/kotlin/lesson2/idiom14-15.kt

@@ -8,9 +8,16 @@ fun String.countOs(): Int = count { it == 'о' } // implicit this points to Stri
 fun main() {
     fun Int.printMe() = println(this) // explicit this
 
-    "обороноспособность".countOs().printMe()
+    "вылысыпыдыстычка".countOs().printMe()
+    
+//    listOf(1, 2, 3).odd
+//    listOf(1, 2.0, 3).odd
 }
 
+//fun doSmth(){
+//    "вылысыпыдыстычка".countOs().printMe()
+//}
+
 /**
  * Extension property (must be virtual)
  */

src/main/kotlin/lesson2/idiom6.kt

@@ -27,7 +27,7 @@ fun main() {
     /**
      * Using singleton reference without constructor invocation
      */
-    val obj = AnObject
+    val obj: AnInterface = AnObject
 
     /**
      * Anonymous object

src/main/kotlin/lesson2/idiom9.kt

@@ -16,8 +16,8 @@ fun findSomething(): Int {
 fun checkCondition(): Int {
     fun conditionSatisfied() = false
 
-    if (conditionSatisfied()) {
-        return 1
+    return if (conditionSatisfied()) {
+        1
     } else {
         //error is Nothing
         error("Condition is not satisfied")

src/main/kotlin/lesson3/idiom16.kt

@@ -28,7 +28,7 @@ fun main() {
         println("a = $a, b= $b, c = $c")
     }
 
-    //Using `let` to compose result. Not recommended to use without a need
+    //Using `let` to compose result. Not recommended using without a need
     val letResult = getAClass()?.let { arg ->
         arg.c + arg.a
     }

src/main/kotlin/lesson3/idiom17.kt

@@ -18,6 +18,7 @@ fun main() {
     fun getAndIncrement() = i.also { i += 1 }
 
     println(getAndIncrement())
+    println(i)
 
     /**
      * Configure properties of an object (apply)

src/main/kotlin/lesson3/idiom18-19.kt

@@ -1,5 +1,7 @@
 package lesson3
 
+import java.util.ArrayList
+
 /**
  * Lists and mutable lists
  */
@@ -14,7 +16,7 @@ fun main() {
     /**
      * This one creates a mutable list
      */
-    val mutableList = mutableListOf("a", "b", "c")
+    val mutableList: MutableList<String> = mutableListOf("a", "b", "c")
     mutableList[2] = "d"
     mutableList.add("e")
     mutableList += "f"
@@ -23,11 +25,11 @@ fun main() {
     /**
      * This one creates a mutable ArrayList.
      */
-    val arrayList = arrayListOf("a", "b", "c")
+    val arrayList: ArrayList<String> = arrayListOf("a", "b", "c")
 
     //Danger zone
 
-    val newList = list + "f" + mutableList
+    val newList: List<String> = list + "f" + mutableList
 
     println(newList)
 

src/main/kotlin/lesson3/idiom20-21.kt

@@ -1,17 +1,25 @@
 package lesson3
 
 fun main() {
-    val map = HashMap<String,String>()
+    val map = mutableMapOf(
+        "key" to "a",
+        "key2" to "b",
+    )
 
     //The map could be accessed via indexing operation
     println(map["key"])
     map["key"] = "fff"
 
 
+    //val entry: MutableMap.MutableEntry<String, String> = map.iterator().next()
+
     /**
      * The destructuring declaration for maps and other objects that support `operator fun componentN`
      */
     for ((k, v) in map) {
+        //val (k, v) = entry
+//        val k = entry.component1()
+//        val v = entry.component2()
         println("$k -> $v")
     }
 
@@ -22,4 +30,8 @@ fun main() {
     val coord = doubleArrayOf(0.0, 1.0, 2.0)
 
     val (x,y,z) = coord
+
+    data class Coordinate(val x: Double, val y: Int)
+
+    val (x1, y1) = Coordinate(1.0,2)
 }

src/main/kotlin/lesson3/idiom22.kt

@@ -1,6 +1,9 @@
 package lesson3
 
 class AClassWithList{
+    var b: Double = 2.0
+        private set
+
     private val _list = ArrayList<Int>()
     val list: List<Int> get() = _list
 }

src/main/kotlin/lesson3/idiom23-24.kt

@@ -1,5 +1,11 @@
 package lesson3
 
+import java.time.Instant
+
+class DateRange(val start: Instant, val end: Instant)
+
+operator fun DateRange.contains(value: Instant): Boolean = value > start && value < end
+
 fun main() {
 
     val emailsList = emptyList<String>()
@@ -15,11 +21,41 @@ fun main() {
         println("not in list")
     }
 
+    println(Instant.now() in DateRange(Instant.EPOCH, Instant.MAX))
+
     // Another (different) use of `in` is iteration over range or collection using
     // using `operator fun iterator`
 
-    for (i in 1..100) { println(i) }  // closed range: includes 100
-    for (i in 1 until 100) { println(i) } // half-open range: does not include 100
-    for (x in 2..10 step 2) { println(x) }
-    for (x in 10 downTo 1) { println(x) }
+    for (i in 1..100) {
+        println(i)
+    }  // closed range: includes 100
+
+    (1..100).forEach { i ->
+        println(i)
+    } //the same, but with boxing
+
+    for (i in 1 until 100) {
+        println(i)
+    } // half-open range: does not include 100
+    for (x in 2..10 step 2) {
+        println(x)
+    }
+    for (x in 10 downTo 1) {
+        println(x)
+    }
+
+    infix fun ClosedRange<Double>.step(step: Double): Sequence<Double> {
+        //TODO check arguments
+        var current = start
+        return sequence {
+            do {
+                yield(current)
+                current += step
+            } while (current <= endInclusive)
+        }
+    }
+
+    for (x in 0.0..10.0 step 0.5){
+        println(x)
+    }
 }

src/main/kotlin/lesson3/idiom25.kt

@@ -26,4 +26,5 @@ fun main() {
     }
     integrate(0.0, PI) { sin(it) }
     integrate(0.0, PI, step = 0.02) { sin(it) }
+    //integrate(0.0, step = 0.02, PI) { sin(it) }
 }

src/main/kotlin/lesson3/idiom26.kt

@@ -6,7 +6,9 @@ fun main() {
     val result = list
         .filter { it % 2 == 0 } //select even numbers
         .map { it * it } // get square of each element
-        .sumByDouble { it.toDouble() } //use one of reduce operations
+        //.onEach { println(it) }
+        //.sumOf { it } //use one of reduce operations
+        .reduce { acc, i -> acc + i }
 
     println(result)
 }